U.S. patent application number 17/437544 was filed with the patent office on 2022-05-26 for spring-damper system.
The applicant listed for this patent is HYDAC MOBILHYDRAULIK GMBH. Invention is credited to Alexander STREIT.
Application Number | 20220161872 17/437544 |
Document ID | / |
Family ID | |
Filed Date | 2022-05-26 |
United States Patent
Application |
20220161872 |
Kind Code |
A1 |
STREIT; Alexander |
May 26, 2022 |
SPRING-DAMPER SYSTEM
Abstract
A spring-damper system consisting of at Least a differential
cylinder (4), a hydraulic accumulator (26) and a control valve
device (1, 2), is characterized in that by means of at least one
motor-pump unit (22) pressure fluid can be supplied to the annular
end (6) or both the annular end (6) and the piston end (8) of the
differential cylinder (4) in a dosed circuit using the control
valve device (1, 2).
Inventors: |
STREIT; Alexander; (Merzig,
DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
HYDAC MOBILHYDRAULIK GMBH |
Sulzbach/Saar |
|
DE |
|
|
Appl. No.: |
17/437544 |
Filed: |
February 26, 2020 |
PCT Filed: |
February 26, 2020 |
PCT NO: |
PCT/EP2020/054997 |
371 Date: |
September 9, 2021 |
International
Class: |
B62D 33/06 20060101
B62D033/06; B60G 11/26 20060101 B60G011/26; B60G 17/04 20060101
B60G017/04; B60G 17/08 20060101 B60G017/08; B60G 99/00 20060101
B60G099/00 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 15, 2019 |
DE |
10 2019 001 855.9 |
Claims
1. A spring-damper system consisting of at least a differential
cylinder (4), a hydraulic accumulator (26) and a control valve
device (1, 2), characterized in that by means of at least one
motor-pump unit (22) pressure fluid can be supplied to the annular
end (6) or both the annular end (6) and the piston end (8) of the
differential cylinder (4) in a closed circuit using the control
valve device (1, 2).
2. The system according to claim 1, characterized in that the
control valve device has two control valves (1, 2), of which in a
fluid-conveying manner one control valve (1) is connected at its
inlet (10) to the annular end (6) and at its outlet (12) is
connected to both the piston end (8) and the inlet (14) of the
second control valve (2), the outlet (16) of which is connected to
the inlet (18) of the pump (20) of the motor-pump unit (22).
3. The system according to claim 1-er-2, characterized in that the
two control valves (1, 2) are proportional throttle valves,
preferably electromagnetically actuatable 2/2-way proportional
throttle valves.
4. The system according to claim 1, characterized in that the
hydraulic accumulator (26) is installed in the connection line (24)
between the outlet (16) of the second control valve (2) and the
inlet (18) of the pump (20).
5. The system according to claim 1, characterized in that a check
valve (34), which opens in the direction of the annular end (6), is
installed in the connection line (32) between the outlet (30) of
the pump (20) and a branching-off point (38) which is connected to
the annular end (6) and to the inlet (10) of the first control
valve (1) in a fluid-conveying manner.
6. The system according to claim 1, characterized in that a
pressure relief valve (36) is installed between the part of the
connection line (32) routed from the outlet (30) of the pump (20)
to the check valve (34), and the connection line (24) routed to the
pressure accumulator (26).
7. The system according to claim 1, characterized in that the
motor-pump unit (22) comprises a gear pump (42), whose leakage oil
port (44) is connected to a return line (46).
8. The system according to claim 1, characterized in that the
outlet (48) of a feed pump (50) is connected to the inlet (18) of
the gear pump (42).
9. The system according to claim 1, characterized in that the
motor-pump unit (22) has a radial piston pump (20) or an orbital
motor is used instead.
Description
[0001] The invention relates to a spring-damper system comprising
at least a differential cylinder, a hydraulic accumulator and a
control valve device.
[0002] Systems of this type are state of the art see EP 2 952 419
A2. Such systems having double-acting suspension cylinders are
preferably used in the cabin suspension systems of vehicles that
are suitable for operation on rough unpaved ground, as is the case
for agricultural or forestry vehicles, construction machinery or
other special vehicles. To protect the cabin crew against impact
loads occurring during operation, cabins of such vehicles are
usually supported against the chassis by double-acting suspension
cylinders. in the known system mentioned above, a proportional 4/2
directional control valve is used to connect the respective
suspension cylinder in the form of a differential cylinder to the
hydraulic accumulator, wherein said proportional 4/2 directional
control valve forms a variable throttle point as a function of its
actuation. By linking the damping valve to the vehicle control
system present in the vehicles concerned, wherein said vehicle
control system contains signal-generating components, such as an
acceleration sensor an and angle sensor, the damping force can be
adjusted to the respective operating conditions to achieve reduced
vibration stress on the cabin.
[0003] Based on this prior art, the invention addresses the problem
of providing a spring-damper system which, while retaining the
advantages achieved in the prior art, is characterized by further
improved operating behavior in comparison to the former.
[0004] According to the invention, this problem is solved by a
spring-damper system having the features of claim 1 in its
entirety,
[0005] According to the characterizing part of claim 1, an
essential feature of the invention is that at least one motor-pump
unit can be used to supply pressure fluid to the annular end or
both the annular end and the piston end of the differential
cylinder in a closed circuit using the control valve device.
[0006] While the known system as a passive system is adaptive in
that the damping strength can be adjusted, the differential
cylinder cannot generate active forces, however; the system
according to the invention can be implemented as an active
suspension system because of the option of an energy supply
initiated by the control valve device by means of the motor-pump
unit. The controlled supply of energy to the annular and/or piston
end of the differential cylinder can be used to influence the
forces in both the compression and rebound directions, unlike in
the known system. Adapting to the conditions of driving operation,
optimum vibration behavior of the cabin can thus be achieved in
accordance with the data supplied by the vehicle sensor system.
[0007] In preferred exemplary embodiments, the control valve device
has two control valves, of which in fluid-conveying manner one
control valve is connected at its inlet to the annular end and at
its outlet is connected to both the piston end and to the inlet of
the second control valve, the outlet of which is connected to the
piston end and to the inlet of the pump of the motor-pump unit. In
this arrangement, the control valve device forms a pressure
regulator which can be used to supply the differential cylinder,
whose piston end in conjunction with the accumulator bears the
static load applied by the vehicle, with additional pressure at the
annular end to generate the additional dynamic forces required for
active suspension.
[0008] Advantageously, both control valves are proportional
throttle valves, preferably electro-magnetically actuatable 2/2-way
proportional throttle valves. They can be actuated directly by the
vehicle electronics resulting in high switching dynamics.
[0009] Advantageously, the arrangement may further be such that the
hydraulic accumulator is installed in the connection line between
the outlet of the second control valve and the inlet of the
pump.
[0010] Advantageously, the arrangement can further be made in such
a way that a check valve, which opens in the direction of the
annular end, is installed in the connection line between the outlet
of the pump and a branching-off point, which is connected to the
annular end and to the inlet of the first control valve in a
fluid-conveying manner. In this way, the differential cylinder is
protected against a pressure drop when the pump is at a
standstill.
[0011] Advantageously, a pressure relief valve can be installed
between the part of the connection line routed from the outlet of
the pump to the check valve, and the connection line routed to the
pressure accumulator, which check valve opens in the direction of
the branching-off point. In this way, the maximum pressure that can
be supplied by the motor-pump unit can be preset.
[0012] Not only are dynamic forces generated in the respective
differential cylinder of the active suspension system according to
the invention, but the static pressure in the differential cylinder
also bears the static cabin load acting thereon. Thus, the pump
arranged in the closed circuit is also pressurized. For a typical
cabin weight in the range of, for instance, 300 kg and a piston rod
diameter of about 18 mm, as is often the case with present cabin
suspension cylinders, this results in a static pressure in the
system of more than 100 bar. Conventional gear pumps, which are
characterized by a high operational reliability and a construction
that is inexpensive to manufacture, are therefore not suitable for
use in this application, as they are only approved for much lower
pressures at the suction end. in an advantageous embodiment,
despite this difficulty, the advantages of a gear pump are made use
of in the invention by using a gear pump in the motor-pump unit,
wherein the Leakage oil port of said gear pump is connected to a
return line. The connection via a leakage oil line to the tank
relieves the pressure at the shaft seal of the gear pump so that it
is pressure-resistant at both ports and it can be used reliably in
the system according to the invention.
[0013] Advantageously, the outlet of a feed pump is connected to
the inlet of the gear pump. This can be used to compensate for
sinking of the cabin caused by the permanent leakage of oil from
the closed circuit to the tank. To be able to maintain the desired
level position and/or for a desired level setting, a proportional
pressure relief valve inserted between the outlet of the feed pump
and the tank can be used to adjust the pressure supplied by the
feed pump. An additional advantage of this arrangement is the
continuous flushing of the closed circuit of the system because of
the leakage and the new oil permanently injected to compensate for
the leakage.
[0014] Alternatively, the motor-pump unit can have a radial piston
pump or instead an orbital motor can be used, i.e. pumps whose
construction permits high pressures at the suction end.
[0015] The invention is explained in detail below with reference to
exemplary embodiments shown in the drawing. In the Figures:
[0016] FIG. 1 shows a symbolic representation of the fluid circuit
of an exemplary embodiment of the spring-damper system according to
the invention;
[0017] FIGS. 2 to 5 show the fluid circuit of FIG. 1, with lines of
different line widths indicating four different main states of the
system of the exemplary embodiment; and
[0018] FIG. 6 shows a symbolic representation of the fluid circuit
of a second exemplary embodiment of the system according to the
invention.
[0019] in the figures, a differential cylinder provided as a
suspension strut, in particular of a cabin suspension, is
designated by the reference numeral 4, has a piston rod designated
by 5 and has working chambers of differently effective piston
surfaces at its annular end 6 and its piston end 8. The annular end
6 and piston end 8 are connected to a control valve device
comprising two control valves, each formed by a proportional
throttle valve. The present exemplary embodiments concern
electromagnetically controlled 2/2-way proportional throttle valves
designated by 1 and 2, respectively. Of these, the proportional
throttle valve 1 at its inlet 10 is connected to the annular end 6
of the differential cylinder 4 and at its outlet 12 is connected to
both the piston end 8 and to the inlet 14 of the second
proportional throttle valve 2. The Latter is connected at its
outlet 16 to the inlet 18 of the pump 20 of the motor-pump unit 22
via a connection line 24. The oil end 28 of a hydropneumatic
pressure accumulator 26 is also connected to the connection line
24. The outlet 30 at the pressure end of the pump 18 is connected
to the annular end 6 of the differential cylinder 4 via a second
connection line 32, in which there is a check valve 34 that opens
in the direction of the annular end 6. A pressure relief valve 36
interposed between a branch point 38 located at the second
connection line 32 between the check valve 34 and the pump outlet
30, and a branch point 40 at the first connection line 24
complements the fluid circuit of the first exemplary embodiment
shown in FIGS. 1 to 5.
[0020] In this arrangement, the piston end 8 of the differential
cylinder 4, in conjunction with the hydraulic accumulator 26, bears
the static load, which can result in a static pressure of more than
100 bar for a standard 3-point support of a cabin weighing 300 kg.
In view of the high-pressure level, the pump 20 of the motor-pump
unit 22 in this example is an axial piston pump, which permits high
pressures at the suction-end inlet 18. Alternatively, an orbital
motor could be used.
[0021] As long as the proportional throttle valves 1 and 2 are not
actuated and are open in their non-throttling home position, the
motor-pump unit 22 does not have to build up any pressure. Apart
from the line resistances, the pump 20 pumps the oil without
pressure difference in the closed circuit containing the
differential cylinder 4, wherein the annular chamber 6 is connected
to the pressure-end outlet 30 of the pump 20.
[0022] The piston end 8 is connected to the outlet 12 of the first
proportional throttle valve 1 and to the inlet 14 of the second
proportional throttle valve 2. As long as both valves 1 and 2 are
in their home position, the static pressure at the annular end 6
and at the piston end 8 is identical, and because they are
interconnected without throttling, the suspension is undamped. In
FIGS. 2 to 5, four main states of the system that occur when the
valves 1 and 2 are actuated, are indicated in that the line
sections bearing the higher pressure, are drawn using a greater
line thickness.
[0023] In the "active compression" state illustrated in FIG. 2, the
first proportional throttle valve 1 is actuated from the open home
position to move to a throttle position. The volume flow generated
by the pump 20 causes a pressure acting in the annular chamber 6 of
the differential cylinder 4 to be built up by the throttling effect
of the actuated valve 1, wherein said built-up pressure gives rise
to an active compression motion of the piston rod 5.
[0024] FIG. 3 refers to the "Active rebound" state. In this state,
the second proportional throttle valve 2 is actuated. As a result
of its throttling effect, a pressure is built up both in the
annular chamber 6 and in the piston chamber 8. Because of the
larger piston surface of piston chamber 8, the increased pressure
in the cylinder 4 causes an active extending motion of the piston
rod 5.
[0025] FIG. 4 refers to the "Damping during rebound" state. In this
state, the piston rod 5 of the cylinder 4 performs an extending
motion. Oil is thus displaced from the annular chamber 6 to the
piston chamber 8 via the open proportional throttle valve 1, which
is not actuated. If the proportional throttle valve 1 is now
actuated, this volume flow builds up and creates a pressure
difference between the annular end 6 and the piston end 8 of the
cylinder 4. This pressure difference has a damping effect during
the extending motion.
[0026] FIG. 5 refers to the "Damping during compression" state. The
piston rod 5 of the cylinder 4 is now in a retracting motion. Some
of the oil flows from the piston end 8 to the annular end 6 via the
non-actuated, open proportional throttle valve 1, The other part
flows into the accumulator 26 via the second proportional throttle
valve 2.1f the second proportional throttle valve 2 is now
actuated, a pressure difference is built up by the volume flow to
the accumulator 26 and counteracts the spring compression in a
damping manner.
[0027] FIG. 6 shows a second exemplary embodiment in which the
closed circuit having differential cylinder 4, control valves 1 and
2, accumulator 26 and pump of motor-pump unit 22 corresponds to the
first exemplary embodiment, The difference, in contrast thereto, is
that instead of the axial piston pump 20, a gear pump 42 having a
leakage oil port 44 is used and the leakage oil port 44 is
connected to a tank 52 via a return line 46 and is thus
non-pressurized. The resulting pressure release of the shaft seal
of the gear pump 42 renders it pressure-resistant at its two ports
and thus safe to operate despite the high pressure Level present in
the closed circuit. However, the leakage oil flow, which can be up
to 1% of the nominal volume flow, causes the piston rod 5 to
continuously subside because of the permanent drain from the closed
circuit to the tank 52. To still be able to maintain the desired
level position, a feed pump 50 in the form of a small gear pump is
provided, which takes in from the tank 52 and generates a feed
pressure at its pressure-end outlet 48, which is connected to the
connection line 24 via a check valve 54. A proportional pressure
relief valve 56, which is installed between the outlet 48 of the
feed pump 50 and the tank 52, can be used to adjust the feed
pressure and thus the level position. An additional advantage of
the embodiment of Fig, 6 is that because of the Leakage and the oil
that is permanently re-injected to compensate for the leakage,
continuously flushes the closed circuit of the system.
* * * * *